Serialization with runtime class loaders

I have a problem with the java serialization.
This is the environment:

- The A program that loads a set of classes (using Class.forName command with custom classloader) and creates new instances for those classes.
All instances will be saved into List<Object> and sended through socket with writeObject method.

- The B program that loads the same set of classes (always in runtime mode, with Class.forName command) and receives the List<Object> from socket with readObject command.

So, the problem is that i receive an exception(ClassNotFoundException) during the readObject method execution. I suppose that when I load all classes at startup, my principal classloader don't uses the new classes (that have their own classloaders).

But, how can i read runtime loaded objects from readObject? How can i tell to readObject to use my additional classloaders?